Piston for internal combustion engines



Aug- 11, 1959 H. RlEsELER 2,898,897

PISTON FOR INTERNAL COMBUSTION ENGINES Filed May 20, 1955 2 Sheets-Sheet 1 l l I/ l i y y i BY HELE/VE RIESELEI?, HE

Aug. 11, 1959 H. RlEsELER 2,898,897

` PISTON FOR INTERNAL COMBUSTION ENGINES Filed May 20, 1955 I 2 Sheets-Sheet 2 27 x48 3b. Amro J4 33 so l j f E22 United States Patent Ofce 2,898,897 PatentedAug. 1l, 1959 PISTON FOR INTERNAL COMUSTION ENGINES Hermann Rieseler, deceased, late of Neidlingen (Teck), Germany, by Helene Rieseler, ne Scherber, heir, Neidlingen (Teck), Germany Application May 20, 11955, Serial No. '509,967 In Germany October 13, 1948 Public Law '619, August 23, 1954 Patent expires October 13, 1968 16 Claims. (Cl. 12S-441.38)

The present invention relates to internal combustion engines and, more particularly concerns pistons for such internal combustion engines.

The increase in the compression ratioand the efficiency of piston-actuated internal combustion. engines results in a corresponding increase in the thermal stress acting upon the pistons.

In order to master these higher thermal stresses, heretofore, in most instances the cross sections of the heat conducting portions were increased or it was attempted to cool the respective piston sections either by directly air cooling, oil cooling or water cooling the piston top. These steps, however, resulted in a corresponding increase in heat losses.

It has also been suggested to protect the piston top against burning through by providing the piston with a protective layer of heat resistant material. It is furthermore known with such shielding arrangements to reduce the heat passage from the re resistant shielding plate to the piston body by providing an air space therebetween.

The above mentioned steps for mastering the thermal stresses to which the piston is subjected are, however, insuicient when internal combustion engines are involved working at high compression, high load and minor quantities of excessive air. Particularly with this last type of internal combustion engines it is not possible to maintain light metal pistons in working condition if they are merely protected in the heretofore known manner.

It is, therefore an object of the prescent invention to provide a piston for use in internal combustion engines which will be able better to withstand high thermal stresses `than heretofore known pistons.

It is another object of this invention to provide a light metal piston for use in connection with internal combustion engines, which will considerably block the heat transfer from the piston top to the piston body.

It is still another object of this invention to provide a piston as set forth in the two preceding paragraphs which will be relatively simple and inexpensive in production. I

These and other objects and advantages of the invention will appear more clearly from the following specification in connection with the accompanying drawings in which:

Fig. 1 illustrates a longitudinal section through a light metal piston according to the present invention.

Fig. 2 is a section taken along the line lI-lI of Fig. 1.

Figs. 3 to 6 illustrate details of the piston shown in Figs. l and 2.

Fig. 7 is a longitudinal section through a modified piston according to the invention.

Fig. 8 shows still another modification of the present invention.

Fig. 9 is a section taken along the line IX-IX of Fig. 8 with additional supply and discharge means connected to the cylinder in which the piston of Fig. 8 is reciprocably mounted.V

General arrangement The primary feature of thepiston .according to the present invention consists in that the piston is provided with a protective cap made of a material considered to be a relatively poor heat conductor c g. rhodium alloy steel. The highly heat resistant piston top is provided with supporting ribs which latter rest upon corresponding ribs of a supporting body interposed between the piston top and the piston body. The ribs of the piston top may rest on the corresponding ribs of the supporting body either directly or through the intervention of an intermediate plate or disc. The piston top which may be arched. outwardly or inwardly consists of a highly heat resistant material, for instance of chromium nickel steel with a high nickel content.

The ribs of the supporting body and the corresponding ribs of the piston top form a plurality of concentrically arranged supporting cylinders which at the same time protect that portion of the protective cap which carries piston rings against the admission of heat by radiation from the piston body which is llame actuated and glows. This heat protection can furthermore be increased by an insert, for instance of thin highly heat resistant steel plate material. The heat transfer by conduction and radiation from the protective cap to the piston body can be reduced by means of a thin steel plate resting on the piston shank.

The outer mantle portion of the protective cap is provided with a skirt or extension extending beyond the abutment surfaces of the protective cap and the piston body. Said skirt is similar to the other portion of the protective cap provided with resilient piston rings which not only seal the working chamber of the piston but also serve for reducing the gas pressure acting upon the surfaces along which the protective cap and the piston body engage each other.

The protective cap may be connected to the piston body in any known manner for instance by means of steel screws. This type of connection, however, especially when employing piston bodies of light metal, is disadvantageous insofar as the heat transfer through the connecting screws to the piston body brings about a non-uniform expansion of the piston body and therefore a reduction in the supporting or effective sliding surface of the piston. This drawback has been overcome according to the present ind vention by providing the outer protective cap mantle with a threaded ring which latter is secured against rotation and consists of a material with the same heat expansion coeicient, said threaded ring resting in an annular recess of the piston body. In order to equalize minor ditferencesof expansion in axial direction, an only slightly resilient insert is provided between the threaded ring for the protective cap and the bearing of the piston body. This insert may consist of a steel pipe, an annular spring or of resilient portions of the threaded ring itself.

In order to carry away the heat which in spite of the above mentioned steps is conveyed to the supporting body for the protective cap and to the piston body, there is according to the present invention, provided a pulsating air How through the piston. This pulsating air ilow is produced by the acceleration of the piston in cooperation with the greatly varying ilow resistances of two channels in the piston body and the continuous change in the direction of movement and the change in the speed aided by the inertia of the air in the piston chamber.

Structural arrangement Referring now to the drawings in detail and Figs. 1 and 2 thereof in particular, the piston shown therein comprises a piston shank 1 which is provided with an annular recess 1a having arranged therein a threaded ring 2. This ring is in any convenient manner prevented from rotation relative to said shank 1. The piston, furthermore, comprises a protective cap 4 which has a skirt 3 threadedly engaging the threaded ring 2. When the protective cap 4 is threaded on said ring 2, said cap 4 abuts a bearing member 6 which is threadedly connected tothe piston shank 1 and presses against a tubular steel spring'S interposed between the ring 2 and the member 6. Interposed between the piston shank 1 and the protective cap 4 is an insert 7 in form of a metallic plate which insert is firmly clamped between the protective cap 4 and the shank 1 when cap 4 is rmly threaded upon the ring 2. Furthermore, a radiation disc 11 may be arranged between the ribs 9 forming concentric annular walls of the supporting body 8 and the ribs 10a connected to the piston top 10 and respectively aligned with the ribs 9.

As has been found by experience, the medium gas temperature will during a working cycle in the piston working chamber at approximately quadruple increase in the output over the nonloaded diesel engine reach a temperature of approximately 80() to 900 C. In order to keep the heat transfer to the top of the piston as low as possible, it is intended to have the piston top assume an approximately high temperature. To this end, the heat conveying cross sections of the protective cap 4 and of the supporting body 8 are dimensioncd so small that the heat which is still conveyed to the protective cap by conduction and radiation can be carried away through the cylinder wall by means of the resilient piston rings 12 arranged in said protective cap 4.

In spite of the reduction of the heat resistance of the piston top material to a permanent loadability of approximately l kilogram per square millimeter, the piston top 10 has due to its shape, and especially due to its supporting ribs 10a aligned with the ribs 9 of the supporting body 8, become so resistant that it will safely be able to withstand combustion pressures up to approximately 150 to 170 kilograms per square centimeter acting upon the piston.

The small quantity of heat conveyed by means of the insert 7 and ring 2 upon the piston shank 1 is carried away by some resilient piston rings in the piston shank.

The chamber 13 between the insert or closing disc 7 and the shank is connected with the larger chamber 16 confined by the piston skirt through two channels 14 and 15. In order better to carry away the heat conveyed by conduction and radiation to the insert 7, shank 1 and the air in the chamber 13, the air present in the channels 14 and 15 and in the hollow chamber 13 may be put in motion in a simple manner by the working of the piston. When pistons are involved which are subjected to particularly high thermal stresses, it is expedient for carrying the heat away to provide guiding members 17 and 18 in front of the mouths of the channels 14 and 15, which guiding members will act in a manner of not completely closing check valves. These guiding members 17 and 18 may either be connected to the piston shank as shown in Fig. l or may be connected to the connecting rod which engages the wrist pin. The blade-shaped guiding members 17 and 18 are respectively curved in opposite directions. These members 17 and 18 and the mouths of the channels 14 and 15 are so shaped that a portion of the air in the chamber 16 can almost unimpededly ow into the channel 14 when the piston is accelerated in one direction whereas in that instance the ow of air into the channel 15 is greatly impeded by the oppositely directed curvature of the guiding member 1S arranged at the mouth of the channel 15, which guiding member 18 brings about a considerable deviation and shielding. When the piston is accelerated in opposite direction, i.e. in upward direction with regard to Fig. l, the discharge of air from the channel 14 into the chamber 16 is greatly impeded by the guiding member 17.V In contrast thereto, the air entrapped in chamber 13 can now almost unimpededly pass through channel 15 and by the guiding member 18.

The acceleration of the piston, the inertia of the air column and the unequal flow resistances at both mouths of the channels 14 and 15 respectively will in this way work in the manner of a double acting air pump with the result that a pulsating air ow will be created from the chamber 16 through channel 14 and chamber 13 through channel 15 back to the chamber 16 of the piston shank. This pulsating air ow considerably contributes to carrying away the heat which passes from the protective cap 4 to the air contents of the hollow chamber 13 and to the piston shank, whereby the thermal loadability of the piston is materially increased.

The insert 7 which serves primarily for preventing the deposit of oil residues and for preventing a coking of the arched inner wall of the supporting body 8 may be omitted when the admission of oil to the chamber 13 ca n be prevented as Vis the case for instance with engines with opposed pistons reciprocable in horizontally arranged cylinders. It is, however, understood that only that portion of the insert 7 is omitted which covers or lextends across the chamber 13. After said portion of the insert 7 has been eliminated, the pulsating air How can engage the inner arch of the supporting body 8 whereby the heat is better carried away from the hottest part of the supporting body with the result that its resistance is improved.

While Fig. 1 shows a light metal piston with protective cap the outer mantle of which is made of one piece with the supporting body, and while the piston top which is arched outwardly is made of particularly high heat resistant material such as high nickel-content chromium nickel steel and is screwed or welded to the protective cap, Fig. 7 shows a light metal piston with protective cap of which the outer mantle is made of one piece with the piston top. The supporting body is in this instance a separate body as 1s clearly shown in Fig. 7. Those parts of Fig. 7 which correspond to similar parts in Fig. 1 are designated with the same reference numeral but with the additional character a.

Referring now to Figs. 8 and 9, the operating temperature, particularly that of the piston walls provided with plston rings, can furthermore be reduced and thereby the safety of operation of pistons isubjected to high thermal stresses can be further increased by passing the above mentioned pulsating flow of cooling means through a piston chamber which is arranged closely behind that mantle portion of the piston which is provided with piston rings and extends over the most essential portion of the piston ring section.

The connection of this chamber with a cooling means conveying pressure conduit is periodically established through the intervention of channels and slots of the piston and through slots in the cylinder bushing, said slots 1n said piston and said cylinder bushing registering with the inlet and outlet slots of the piston in one or both dead center positions of said piston. In this way the employment of telescopic connecting tubes and the drawbacks inherent thereto have been avoided.

As will be seen from Fig. 8, the piston shown therein is provided with a narrow chamber 19 which extends over the major portion of the piston ring section. The charnber 19 communicates with the inlet slots 20 through passage 21 and pocket 22 and furthermore communicates with the discharge slots 23 through passage 24 and pocket 25.

Referring to Fig. 9, this figure shows the piston shank 26 in the outer, i.e. lower dead center position of the piston `in which the piston inlet slots 20 register with the inlet slots 27 in the cylinder bushing 38 and with slots 39 in the cylinder block 40 for -the admission of cooling means while the discharge slots 23 in the piston register with the discharge slots 29 in the cylinder bushing and with slots 41 in the block 40. The connection or hood 30 connected to the cylinder via an intermediate tube 42 communicates with a cooling means conveying pressure conduit 43, for instance with scavenging air conveying pressure conduit or with the pressure conduit conveying the lubricating oil for lubricating the motor. Similarly the cylinder has connected thereto a discharge connection or hood 44 secured to the intermediate tube 31 and extending into the outlet conduit 45. The arrangement is such that the passage 43, 30, 42, 39 and 27 and the passage 29, v41, 31, A44, `45 is provided twice in two different heights, so that the upper passage registers with the slots 20 of the piston when the latter is in its upper dead center position.

If, for purposes of further improving the cooling of the piston ring section it is desired to eliect communication between the chamber 19 and the cooling means conveying pressure conduit of the motor not only in the outer but also in the inner dead center position of lthe piston, the cylinder mantle is provided with two delivery hoods 30 and cylinder slots 27 and is further provided with two discharge hoods 31 with the discharge slots 29 pertaining thereto. The respective inlet slots and respective outlet slots are spaced from each other by a distance equaling the piston stroke. IIn this instance the piston shank is provided with two extensions which in the outer (lower) dead center position of the piston cover the outer cylinder slots.

The inner piston chamber 32 which is somewhat similar to the chambers 7 and 7a of Figs. l and 3 communicates through passage 33 with the inlet channel 34 and furthermore communicates through passage 35 with the channel 36 carrying away the heat.

The two piston pockets 22 and 25 may, similar to cast pistons, consist of a single piece with the piston shank or, as shown in the drawing may form a separate piece which is inserted into the mantle of the piston shank and is connected thereto by a spring ring 37 or in any other convenient manner. f

It will be understood that the employment of a chamber closely behind the piston ring section and the passing of a pulsating flow of cooling means therethrough is not limited to pistons subjected to particularly high thermal stresses. The employment of the last mentioned hollow chamber and the passing of a pulsating ilow of cooling means may also advantageously be applied to pistons subjected to less high thermal stresses inasmuch as also in such instance the safety against seizing by burning, particularly of the piston rings near the piston top will be considerably increased.

Itis, of course, to be understood that the present invention is, by no means, limited to the particular constructions shown in the drawings but also comprises any modications within the scope of the appended claims.

What is claimed is:

1. A multiple part piston for internal combustion engines, which comprises in combination: a main piston body, a piston top body having at least its top portion made of highly heat resistant but a relatively poorly heat conducting material so that the piston top will glow during vthe operation of said piston, said piston top body comprising relatively long and narrow reinforcing ribs, a supporting body interposed between said main body and said piston top body and provided with supportingwalls substantially aligned with said ribs and supporting the same, and means associated with at least two of said bodies for rmly securing all of said bodies together.

2. A multiple part piston according to claim l, in which said ribs form a plurality of annular bodies concentrically arranged in spaced relationship to each other, and in which said supporting walls likewise form concentrically arranged annular bodies aligned with said annular bodies formed by said ribs.

3. A multiple part piston for internal combustion engines, which comprises in combination: a main piston body, a piston top body having at least its top portion made of highly heat resistant but a relatively poorly heat conducting material so that the piston top will glow during the operation of said piston, said piston top body comprising relatively long and narrow reinforcing ribs, a supporting body interposed between said main body and said piston top body and provided with supporting walls 6 substantially aligned with said ribs and supporting the same, steel plate means interposedy between said' ribs and said-supporting walls for reducing the heat transfer from said ribs to said walls, and means associated with at least two of said bodies for rmly securing all of said bodies together and rmly securing said plate means between said ribs and said supporting walls.

4. A multiple part piston for internal combustion engines, which comprises in combination: a main piston body of light metal, a piston top body having at least its top portion made of highly 'heat resistant but a relatively poorly heat conducting material Iso that the piston top will glow during the operation of said piston, said piston top body comprising relatively long `and narrow reinforcing ribs, a supporting body interposed between said main body and said piston top body and provided with supporting walls substantially aligned with said ribs and arranged for supporting the same, a heat conducting steel plate insert between said main piston |body and said supporting body, and means 4associated with at least two of said bodies for firmly securing all of said bodies together.

5. `A multiple part piston for internal combustion engines, which comprises in combination: a main piston body, a piston top body having at least its top portion made of highly heat resistant but a relatively poorly heat conducting material so that the piston top will glow during the operation of said piston, said piston top body comprising reinforcing ribs, a supporting body interposed between said main body and said piston top body and provided with supporting walls substantially aligned with said ribs and supporting the same, said supporting body being providedwith skirt means surrounding a portion of said main body and having grooves in the peripheral surface of said supporting body for receiving piston rings, and means associated with lsaid bodies for firmly securing all of said bodies together.

6. A multiple part piston for internal combustion engines, which comprises in combination: a main piston body, a piston top body having at least its top portion made of highly heat resistant but a relatively poorly heat conducting material so that the piston top will glow during the operation of said piston, said piston top body comprising reinforcing ribs, a supporting body interposed between said main body and said piston top body and provided with supporting walls substantially aligned with said ribs and arranged for supporting the same, said piston top body being provided with skirt means sur- Irounding a portion of said main piston vbody and having its peripheral surface provided with grooves for receiving piston rings, and means associated with at least two of said bodies for firmly securing .all of said bodies together.

7. A multiple part piston for internal combustion engines, which comprises in combination: a main piston body, a protective body including a piston top section having at least its top portion made of a highly heat resistant but a relatively poorly heat conducting material so that the top portion will glow during the operation of said piston, said piston top section being provided with reinforcing ribs, said protective body also including a supporting member interposed between said main piston bodyand said piston top section and provided with supporting walls substantially aligned with said ribs and arranged for supporting the same, that end of said proteotive body which is rremote from said piston top section being provided with a threaded section, a threaded ring xedly connected to said main piston body and arranged for threadedly engaging said threaded section of said protective Ibody, and means carried by said main piston body and interposed between said supporting member and said threaded ring for abutment with the latter.

8. A multiple part piston for internal combustion engines, which comprises in combination: a main piston body, .a protective body including la piston top section having at least its top portion made of a highly heat resistant but a relatively poorly heat conducting material so that the top portion will glow during the operation of said piston, said piston top section being provided with reinforcing ribs, said protective body also including a supporting member interposed between said main piston body and said piston top section and provided with supl porting walls substantially aligned withfsaid ribs and arranged for supporting the same, that end of said protective body which is remote from said piston top section being provided with a threaded section, a threaded ring fixedly connected to said main piston body and arranged for threadedly engaging said threaded section of said protective body, abutment means carried by said main piston body for engagement with said supporting member, and resilient means interposed between said threaded ring and said abutment means.

9. A multiple part piston for internal combustion engines, which comprises in combination: a main piston body having a skirt at one end thereof confining first chamber means, the other end of said piston body being provided with second chamber means, first and second conduit means respectively extending through said main piston body in spaced relationship to each other and effecting communication between said first and -second chamber means, means respectively arranged within said first chamber means adjacent the points of communication of the latter with said first and second conduit means respectively for guiding air in said first chamber means to circulate from said first chamber means through said first conduit means into said second chamber means and from there through said second conduit means into said first chamber means, a piston top body having at least its top portion made of highly heat resistant but a relatively poorly heat conducting material so that the piston top will glow during the operation of said piston, said piston top tbody comprising reinforcing ribs, a supporting body interposed between said main body and said piston top body and provided with supporting walls substantially aligned with said ribs and supporting the same, and means associated with at least two of said bodies for firmly securing all of said bodies together.

l0. A multiple part piston according to claim 9, which includes a thin steel plate insert interposed between said main piston body and said supporting body, and in which said second chamber means is confined by said insert and an adjacent c avity in said main piston body.

ll. A multiple part piston for internal combustion engines, which comprises in combination: a main piston body having a skirt at one end thereof confining first chamber means, the other end of said piston body being provided with second chamber means, first and second conduit means respectively extending through said main body in spaced relationship to each other and effecting communication between said first and second chamber means, guiding means respectively arranged within said first chamber means adjacent the points of communication of the latter with said first and second conduit means respectively for guiding air in said first chamber means to circulate from said first chamber means through said first conduit means into said second chamber means and from there through said second conduit means into said first chamber means, said guiding means comprising a first deector member having an arched section facing away from the point of communication of said first conduit means with said first chamber means to guide air in said first chamber means into said first conduit means, said guiding means also comprising a second deliector member having an arched section directed toward said second conduit means to guide air from the latter about the last mentioned arched section While deflecting air in said first chamber means away from the point of communication of said second conduit means with said first chamber means, a piston top body having at least its top portion made of highly heat resistant but a relatively poorly heat conducting material so that the piston top 8 will glow during the operation of said piston, said piston top body comprising reinforcing ribs, a supporting body interposed between said main body and said piston top body and provided with supporting walls substantially aligned with said ribs and supporting the same, and means associated with at least two of said bodies for firmly securing all of said bodies together.

l2. A multiple part piston for internal combustion engines, which comprises in combination: a main piston body, a protective body connected to said main piston body and including a piston top member having at least its top portion made of a highly heat resistant but poorly heat conducting material so that the piston top will glow during the operation of said pison, said piston top member comprising reinforcing ribs, said protective body also including a supporting member interposed between said main piston body and said piston top member and provided with supporting walls substantially aligned with said ribs and arranged for supporting the same, said pro tective body also comprising a skirt section provided with grooves for receiving piston rings, cooling chamber means confined by said skirt section and one end of said main piston body, first conduit means extending through said main piston body and having one end thereof in communication with said cooling chamber means and having its other end arranged for communication with a cooling means supply passage, and second conduit means extending through said main piston body and having one end in communication with said cooling chamber means and having its other end arranged for communication with a cooling means exhaust passage.

13. A multiple part piston according to claim l2, which includes an additional cooling chamber means located partly in said protective body and partly in the adjacent end portion of said main piston body, said multiple part piston also including passage means respectively establishing permanent communication between said additional cooling chamber means and said first and second conduit means.

14. A multiple part piston for internal combustion engines, which comprises in combination: a main piston body, a protective body connected to said main piston body and including a piston top member having at least its top portion made of a highly heat resistant but poorly heat conducting material so that the piston top will glow during the operation of said piston, said piston top member comprising reinforcing ribs, said protective body also including a supporting member interposed between said main piston body and said piston top member and provided with supporting walls substantially aligned with said ribs and arranged for supporting the same, said protective body also comprising a skirt section provided with grooves for receiving piston rings, cooling chamber means confined by said skirt section and one end of said main piston body, first conduit means extending through said main piston body and having one end thereof in cornmunication with said cooling chamber means and having its other end arranged for communication with a cooling means supply passage in said main piston body, second conduit means extending through said main piston body and having one end in communication with said cooling chamber means and having its other end arranged for communication with a cooling means exhaust passage, and insert means inserted in said main piston body and respectively forming connecting channels for connecting said first and second conduit means with said cooling means supply and discharge passages respectively.

15. In combination in a cylinder piston arrangement: a cylinder having slot means arranged for respectively admitting and discharging cooling means, a multiple part piston arranged in said cylinder and movable relative thereto, said piston being provided with slot means for respectively communicating with the slot means of said cylinder, the arrangement being such that communication of said .cylinder slot means with the slot means of said piston being effected when said piston is at least near one of its dead center positions, said piston being composed of a main piston body and of a protective body connected thereto, said protective body comprising a piston top member having at least its top portion made of a highly heat resistant but poorly heat conducting material so that the piston top will glow during the operation of said piston, said piston top member comprising reinforcing ribs, said protective body also including a supporting member interposed between said main piston body and said piston top member and provided with supporting walls substantially aligned with said ribs and arranged for supporting the same, said protective body also comprising a skirt section provided with grooves for receiving piston rings, cooling chamber means confined by said skirt section and one end of said main piston body, and first and second conduit means extending through said main piston body and respectively electing communication between said cooling chamber means and said admission and discharge slot means of said piston.

16. In a cylinder piston arrangement having a cylinder provided with a lirst pair of cooling means supply and discharge slots and a second pair of cooling means supply and discharge slots spaced from said first pair by a distance equaling the stroke of the piston in said cylinder piston arrangement, said piston comprising in combination: a main piston body, a protective body, said protective body including a piston top member having at least its top portion made of a highly heat resistant but poorly heat conducting material so that the piston top will glow during the operation of said piston, said piston top member comprising reinforcing ribs, said protective body also including a supporting member interposed between said main piston body and said piston top member and provided with supporting walls substantially aligned with said ribs and arranged for supporting the same, said protective body also comprising a skirt section provided with grooves for receiving piston rings, cooling chamber means confined by said skirt section and one end of said main piston body, and rst and second conduit means having one end thereof respectively in cornmunication with said cooling chamber means and having their other ends arranged for communication with inlet and outlet slots respectively in said main piston body.

References Cited in the le of this patent UNITED STATES PATENTS 1,223,622 Schmidt Apr. 24, 1917 1,783,054 Radlotf Nov. 25, 1930 2,266,192 Grieshaber Dec. 16, 1941 FOREIGN PATENTS 300,113 Germany Sept. 15, 1919 487,377 Great Britain June 20, 1938 

